The compiled CSS you're talking about isn't the issue, the compile css loads after everything else, so it has to wait for all your other content to be loaded beforehand. That's why when you run a test such as Pingdom, it may be listed as taking X seconds to load but thats only after all your images and plugins have been loaded.

If you go to the URL for your compiled CSS, it loads instantly.

I ran a test of my own and found that you're using shared hosting and there are 166 websites hosted on the same server as you. It you're concerned about performance, then I would recommend upgrading to a new package such as a VPS or Ded Box, or changing host.

To gzip your compiled CSS you will have to turn the file mode on by adding the following to wp-config.php

Over optimisation will actually slow your site down, especially as you have opted to use disk based object/database and page caching, most cheap shared hosts used network filesystems and are slow as custard.